Scientists say the discovery of a resistant tree is the ‘first large step’ in fighting the disease.
Photograph: Gareth Fuller/PA

She has a silver-grey trunk, is 200-years-old and unusually resilient. Betty, a mature ash tree in Norfolk, is offering hope that ash dieback disease will not be as destructive as first feared after scientists identified her “strong tolerance” to the disease.

Researchers from a government-backed consortium of universities and research centres have developed three genetic markers to enable them to predict whether a tree is likely to be tolerant to the disease, raising the possibility of using selective breeding to develop strains of disease-resistant trees.

Scientists for the Nornex consortium, a group of researchers led by the John Innes Centre, produced genome sequences for two tolerant Danish trees and established three markers which they believe are predictive of a tree’s ability to shrug off the fungal disease.

One researcher’s computer “collapsed” under the weight of the data processed as 248 trees were tested from the Norfolk woodland, which experienced “a massive fungal infection” of ash dieback, according to the researchers.

The scientists predict that 3% of British ash trees will show a fairly high level of tolerance to the fungal disease – a degree of resistance believed to be significantly higher than on the continent. The disease has killed 90% of the ash trees in Denmark but scientists at the John Innes Centre predicted that could now be reduced to 50% in Britain.

“She’s named Betty for her tolerance and resilience,” said Lord Gardiner, spokesperson for the Department for Environment, Food and Rural Affairs in the Lords. “We want to guarantee the graceful ash tree continues to have a place in our environment for centuries to come and this vital work is a major step towards ensuring just that.”

Betty was named by Ann Edwards of the John Innes Centre who first identified the outbreak in Ashwellthorpe. “It’s been an emotional roller coaster. I spent the whole of 2012 being really sad. Now something positive has come out of it, I feel much better,” she said.

Just three metres from Betty is a sapling which has copper-coloured stains on its trunk, showing it is dying from the disease. Further away, an ash tree called Clarence has died. But Edwards pointed to another younger tree which is so far surviving despite being just centimetres from a completely dead ash. “This could be one of Betty’s children – it could be Charles,” she said.

What researchers don’t yet know is whether a super-tolerant tree such as Betty produces super-tolerant offspring. Edwards is hopeful because Betty’s flowers are likely to be pollinated by an “exceptionally healthy-looking” male tree called Donald nearby.

Betty produced a huge seed crop this spring but most of it was blown away by Storm Katie before it could be collected.

The genetic markers, however, can now be used to quickly test and select other ash trees across the country.

Professor Allan Downie of the John Innes Centre and coordinator of the Nornex consortium called the identification of genetic markers “a large first step” in fighting the epidemic.

But he said it was a race against time to identify a wide genetic mix of genetically-tolerant ash trees before the next deadly threat – the emerald ash borer beetle – strikes. The ash borer is moving quickly westwards through Russia and is now top of the UK’s plant risk register, which now counts 811 pests and diseases threatening trees and plants.

“We can’t fix both problems simultaneously. We have to build the ash population up again,” said Prof Downie. “There’s some urgency to make sure we’ve got a healthy population of ash trees so that if, or when, the ash borer gets here we will find some trees with a resistance to it.”

The Nornex report and all data is freely available to other scientists and the public. Prof Downie said he hoped an effort by citizen scientists and wildlife charities to plant and grow potentially disease-resistant ashtrees will quicken the fightback against the disease.

Ash dieback was first identified in Britain in 2012 and is thought to have arrived via imported saplings and by spores carried on the wind from Denmark, where the fungal disease has already killed 90% of its ash trees. Within three years, the disease has spread to the Lake District, Scotland, Wales and the south-west.

“This unprecedented work conducted by British scientists has uncovered an exciting development in tree health,” said Nicola Spence, UK Chief Plant Health Officer. “It paves the way for tackling this destructive disease and will help ensure that Britain’s stock of ash trees, and its countryside, remains resilient against pests and disease in the future.”

Professor Steve Woodward of the University of Aberdeen welcomed the report and said it was possible that British ash trees showed more resistance to the disease because they originated from western rather than eastern Europe after the last ice age. He said: “A rate of 3% of trees showing tolerance doesn’t sound high but ash does seed prolifically so perhaps survivors will eventually fill some of the gaps left by more susceptible individual trees.”